Cancer is typically treated with either chemotherapy and/or radiation therapy. While often effective to destroy a significant amount of tumour cells, such therapies often leave behind a number of tumour cells that are resistant to the treatment. These resistant cells can proliferate to form new tumors that are then resistant to treatment. The use of known combinations of chemotherapeutic drugs has given rise to multidrug resistant (‘MDR’) tumour cells.
The mode of proliferative diseases, such as cancer, is multi-factorial. For instance, research over the last forty years has led to the realisation that cytotoxic agents (or anti-proliferative agents) includes anti-metabolic agents which interfere with microtubule formulation, alkylating agents which are able to cross-link DNA, platinum based agents which are able to interfere with DNA alkylation by blocking DNA replication, antitumor antibiotic agents, topoisomerase inhibitors, etc. In the treatment of such diseases drugs with different mechanisms may be combined (i.e, combination therapies) with beneficial effects including the effective treatment of MDR tumour cells and the minimisation of side effects such as undesirable cytotoxicity. The difficulty here is though that not all known antiproliferative agents provide useful or beneficial effects in combination and accordingly research in many laboratories is presently focused on developing new and useful anti-proliferative combination partners.